Novel electroluminescent polymers with fluoro groups in vinylene units

New electroluminescent polymers with fluoro groups in vinylene units, poly(p-phenylenedifluorovinylene) (PPDFV) and poly(2-dimethyloctylsilyl-p-phenylenedifluorovinylene) (DMOS-PPDFV), have been synthesized by GILCH polymerization. These polymers have been used as the electroluminescent (EL) layers in double-layer light-emitting diodes (LEDs) (ITO/PEDOT/polymer/Al). PPDFV shows photoluminescence around lambda(max) = 580 nm (exciting wavelength, 410 nm) and yellow electroluminescence around lambda(max) = 565 nm. DMOS-PPDFV shows PL around lambda(max) = 495 nm and green EL around Am = 540 nm. The current-voltage-luminance (I-V-L) characteristics of the polymers show turn-on voltages of 3.0 V approximately. Two fluoro groups were introduced on every vinylene units of poly(p-phenylenevinylene) (PPV) and poly(2-dimethyloctylsilyl-1,4-phenylenevinylene) (DMOS-PPV) to give PPDFV and DMOS-PPDFV in an attempt to increase the electron affinity of the parent polymer. It was found that the efficiency of PLED of DMOS-PPDFV was about 7 times higher than that of DMOS-PPV.